Method for eliminating detonation in an engine

ABSTRACT

A method eliminates detonation in an internal combustion engine ( 10 ) by identifying conditions that identify the imminence thereof. The method centers about the pressure inside the cylinder ( 16 ) of the internal combustion engine ( 10 ). The method tracks the pressure and when small rapid changes or fluctuations ( 38 ) in the pressure occur, the ignition timing is advanced for that particular cylinder ( 16 ). An alternative method utilizes a model of pressure based on an array of inputs and how the pressure should act based thereon. The method may also be used to maximize performance of the output of each cylinder ( 16 ) by retarding the ignition timing until the small fluctuations ( 38 ) appear. The ignition timing could immediately be advanced to prevent a detonation thus identifying a maximized output performance without reaching a detonation condition.

BACKGROUND ART

1. Field of the Invention

The invention relates to detecting detonation in an internal combustionengine. More specifically, the invention relates to preventingdetonation in an internal combustion engine by identifying conditionsrelating to detonation.

2. Description of the Related Art

Internal combustion engines used in motor vehicles require detonationdetection. Detonation, more commonly referred to as “engine knock,” isan event occurring in a cylinder of the motor vehicle wherein the fuelinside the cylinder is prematurely detonated. The result of thepremature detonation is a loss of power and an increase of pollutantsbeing released thereby.

OEM systems vary in how they detect and avoid detonation of the fuel.Regardless of the method used, they all have the advantage ofincorporating the required technology directly into the internalcombustion engine. For example, if a particular method requires a sensorto determine engine block vibrations, one could be installed as originalequipment.

None of the systems know are capable of being implemented after market.More specifically, none of the systems are capable of being implementedbecause they are either environment specific, i.e., designed to aspecific internal combustion engine, or they require technology thatcannot be implemented after the manufacture and assembly of the internalcombustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view partially cut away of an internalcombustion engine incorporating one embodiment of the invention;

FIG. 2 is a side view of a spark plug;

FIGS. 3A and 3B are graphs of cylinder torque generated by a cylinder ofan internal combustion engine as a function of torque generation; and

FIG. 4 is a logic flow chart of one method according to the invention;

FIG. 5 is a logic flow chart of an alternative method according to theinvention; and

FIG. 6 is a logic flow chart of a second alternative method according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a perspective view partially cut away of an enginefor a motor vehicle is generally indicated at 10. The engine 10 is aninternal combustion engine. The internal combustion engine 10 mayinclude a distributor 12 or, in the alternative, it may include anelectronic set up more appropriate for operation with an electronic fuelinjector system (neither shown). The internal combustion engine 10 iscontrolled by an engine control unit 14. The engine control unit (“ECU”)14 provides all electrical and electronic communication between thevarious subsystems of the internal combustion engine 10 and othersystems of the motor vehicle (none shown). The ECU 14 will be describedin greater detail subsequently. The internal combustion engine 10includes a plurality of cylinders 16, each having a piston 18 and atleast one intake 20 and exhaust 22 valves. A camshaft 24 moves thevalves 20, 22 and the pistons 18 move a crankshaft 26.

Referring to FIG. 2, a spark plug is generally shown at 28. A spark plug28 is mounted to the internal combustion engine 10 such that a spark end30 thereof is exposed to the interior of one of the plurality ofcylinders 16. At least one spark plug 28 is associated with each of theplurality of cylinders 16. The spark plug 28 provides a spark to ignitethe fuel that has entered each of the cylinders 16 at a time dictated bythe ECU 14 via the distributor 12.

The spark plug 28 also includes a transducer 32. The transducer 32 isdisposed adjacent the spark end 30 of the spark plug 28. The transducer32 is designed to measure the pressure of the gases in the cylinder 16to which the spark plug 28 and transducer 32 are associated. Thereadings from the transducer 32 are transmitted to the ECU 14. It may beappreciated by those skilled in the art that the transducer 32 may be anindependent device that would be secured to the interior of the cylinder16 independently of the spark plug 28. The combination of the spark plug28 and the transducer 32 is one merely of convenience as the port andcurrent available to the spark plug 28 are suitable for the transducer32.

The ECU 14 reads the signals sent by the transducer 32. A typicalreading is shown in the graph of FIG. 3A. The graph shows pressure tobuild within a cylinder 16 until ignition (shown at region 34), afterwhich the pressure drops off as the piston 18 is forced away from itstoo dead center position. This graph represents a normal ignition eventin a cylinder 16 as a function of the torque generated by that cylinder16. In one embodiment, the mean effective pressure is measured.

Referring to FIG. 3B, the pressure graph is shown when a detonationoccurs prior to any ignition in a particular cylinder 16. Detonation isthe combustion of the fuel prior to the time at which it is supposed tobe ignited. A detonation destroys all ability for a cylinder 16 togenerate power. A large fluctuation 36 occurs near region 34 of FIG. 3Arepresenting a detonation. These large fluctuations 36 may vary greatlyin amplitude greatly. Therefore, the large fluctuations 36 shown in FIG.3B are shown having an amplitude that is merely an example amplitude.Immediately preceding the large fluctuation in pressure is a region 38of small fluctuation. This region 38 is sometimes referred to as a smallfuzzy region.

The method of the invention uses the signal from the transducer 32 todetermine whether the region 38 of small fluctuation exists. If so, itcan then be determined that detonation will occur shortly thereafteralong the pressure curve. If the region 38 of small fluctuations isdetected, the ignition timing can be retarded to avoid the occurrence ofthe detonation. This method is therefore capable of detecting when eachof the plurality of cylinders 16 is approaching detonation. Timing foreach of the plurality of cylinders 16 can then be individually advancedor retarded depending on the pressure detection.

More specifically, and with reference to FIG. 4, the method includes thestep of starting and operating the internal combustion 10 at 40. Theamplitude of pressure within a cylinder 16 is measured. In the preferredembodiment, the pressure in each of the cylinders 16 of the internalcombustion engine 10 is measured. Amplitude is measured over time andthe rate of change is calculated at 44.

To determine whether detonation is to occur in a cylinder 16, the ECU 14constantly reviews the rate of amplitude of pressure to identify whenthe rate increases or decreases rapidly. This step, performed at 46, isused to identify when small fluctuations in the amplitude 38 occur. Thisregion of small fluctuations 38 is the precursor to detonation, region36 of large fluctuations in pressure amplitude. Once identified, theignition timing is advanced allowing the internal combustion engine 10to avoid detonation in that particular cylinder 16.

In an alternative embodiment shown in FIG. 5, differences are measuredagainst a model of how pressures within the cylinder 16 are to act givencertain parameters. If the difference at any time exceeds a particularvalue for a particular time, the ignition timing would be advanced toavoid a detonation. In this embodiment, the model may be merely thevalues illustrated in FIG. 3A. Conversely, the model may be moreelaborate and require inputs from various elements of the motor vehicle.By way of example and to be in no way interpreted as limiting, thetorque output and the revolutions per minute of the internal combustionengine 10 are two inputs that could affect how the model would operate.

An added feature of the method for detecting detonation for theprevention thereof is the ability to retard the ignition timing of aninternal combustion engine 10 until the region of small fluctuations 38appears. As shown in FIG. 6, it will be at this point that the maximumamount of performance may be extracted from the internal combustionengine 10 without generating a detonation. Once the small fluctuations38 are detected, the ignition timing is advanced slightly to preventdetonation from occurring.

The invention has been described in an illustrative manner. It is to beunderstood that the terminology which has been used is intended to be inthe nature of words of description rather than of limitation.

Many modifications and variations of the invention are possible in lightof the above teachings. Therefore, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed.

1. A method for preventing detonation of fuel within a cylinder of aninternal combustion engine wherein the cylinder includes a spark plugoperating on an ignition timing, a port and a pressure transduceraccessing the cylinder via the port, the method comprising the steps of:operating the internal combustion engine; measuring the amplitude ofpressure within the cylinder as a function of time; calculating a rateof pressure change; identifying a region of pressure change increasesand decreases that occur rapidly; and advancing the ignition timing ofthe fuel within the cylinder to avoid detonation.
 2. A method as setforth in claim 1 including the step of measuring the amplitude ofpressure change between a peak and a valley in the amplitude of pressuremeasurement.
 3. A method as set forth in claim 2 including the step ofrecording an occurrence of small fluctuations when the rate of pressureamplitude is identified as changing rapidly.
 4. A method as set forth inclaim 3 including the step of recording an occurrence of detonation whenthe rate of pressure amplitude is identified as changing rapidly andwhen the amplitude of pressure between peak and valley is greater than apredetermined value.
 5. A method for optimizing performance of aninternal combustion engine having at least one cylinder wherein thecylinder includes a spark plug operating on an ignition timing, a portand a pressure transducer accessing the cylinder via the port, themethod comprising the steps of: operating the internal combustionengine; measuring the amplitude of pressure within the cylinder as afunction of time; calculating a rate of pressure change; retarding theignition timing of the fuel within the cylinder; identifying a region ofpressure change increases and decreases that occur rapidly; and stoppingthe step of retarding the ignition timing when the rate of pressurechange increases or decreases rapidly.
 6. A method as set forth in claim5 including the step of advancing the ignition timing a predeterminedangle after the step of stopping to ensure detonation does not occur.